The government is in the process of updating forms and procedures to reflect tax law changes mandated by the American Taxpayer Relief Act, and those changes will be complete before Jan. 30, the IRS said.

Forms required of taxpayers filing complex returns that claim residential energy credits, depreciation of property or general business credits will take longer to update. Those taxpayers likely will be able to file beginning in late February or early March, the IRS said.

"We have worked hard to open tax season as soon as possible," said IRS Acting Commissioner Steven T. Miller. "This date ensures we have the time we need to update and test our processing systems."

The IRS will not process paper tax returns before Jan. 30, and there is no advantage to filing on paper before that date. Taxpayers will receive their tax refunds faster by using e-file with direct deposit, the IRS said in a prepared statement.